Re: [Caml-list] Expressing module sig and impl in mli file

[Malcolm Matalka <mmatalka@gmail.com>]

Yes I think I'm confused.  In all parts of this module I want the
Identifiable behaviour, but at the same time I want a Map of these
identifiers to something, so this turned in to me trying to jerry-rig
that rather than thinking about what I actually want.

Can something that is Identifiable be the key to a Map (in Core)?  Am
I doing something wrong if I want that?

Thanks

/M

On Wed, Sep 19, 2012 at 9:11 AM, David House <dmhouse@gmail.com> wrote:
> The standard way of doing this is as follows (note that Identifier is
> changing to Identifiable in the next version, so I'll use that
> terminology):
>
> module Bar : sig
>   type t = string
>   include Identifiable with type t := t
> end
>
> But if this is literally what you're doing, I'm sort of confused. The
> point of identifiable is that you have explicit to_string/from_string
> functions and the type equality with string is not exposed. E.g. you
> might want to use a different comparison function than string
> equality. If you expose the type equality with string, then people are
> free to use String.compare on your type, so you don't get the
> abstraction you wanted.
>
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